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The Hummer Knowledge Base
We all love our Hummers, but all of us say at one time or another "If only they had done this" or "It should have come from the factory with this." Some of the desires are cosmetic, some enhance the toughness of the vehicle and some I will classify as necessary to make the truck livable. I picked up my Hummer (95 gas red wagon) at the end of March.
I bought my truck to be my everyday run-around vehicle. After driving it a few days I made the realization that as much as I love the truck I couldn't live with the noise. As all you Hummer owners know you can't hear the radio (volume on 18) or talk to a passenger without yelling while under way. I'm a person that never complains but, I actually had headaches and was nauseous. I started experimenting with earmuffs used for shooting and regular ear plugs. I even tried the noise cancellation earphones offered by Sharper Image. These actually worked except for the fact that every time you hit a bump a crackle of static surged through the phones and the battery drains rapidly. As you well know with everyone already eyeing your Hummer, wearing earphones really gets weird looks.
Noise in vehicles emanates from a number of places: tires, outside ambient traffic, wind, engine, exhaust, and transmission drive train rotation.
I did learn a few things while using the noise cancellation phones. With the truck parked and running I would put the phones on and they would cancel out all of the existing noise which at this point was just the engine. Surprisingly, it made a major difference that led me to pursue quieting the engine as my first goal. I also learned that the tire tread noise that is at the low end of the frequency spectrum had a component that was causing the nausea. After about 500 miles this noise disappeared. I think once the treads wore in a little the tires ran quieter. Note that the gas Hummer's come equipped with Wrangler GSA's that have a less aggressive tread then the diesels have.
To make your truck quiet here's what you need.
You can get the Thermo-Tec stuff from:
Here's what you do. Clean off the bottom and exhaust pipes real well. Get all of the dirt out from under the truck body. Follow the directions on the insulating wrap and wrap the exhaust system from the point where the exhaust manifold meets the exhaust pipe to as far back as you can go. A careful job may take 8 hours to do. I did my truck over a couple of days working under it with a creeper. It pays to take your time. You do not want this stuff to fall off. When wrapping I found that a 10 foot length was about the longest manageable piece. Take the cut piece and run it quickly through a bowl of water using your fingers to squeegee off the excess water. Don't get the wrap too wet. Wrap very neat and tight with overlap. If possible terminate the strips at the exhaust system joints. This will allow easier maintenance if the exhaust system has to be serviced. Use a lot of clamps. They are easy to use and cut with a regular scissors. Don't wrap the catalytic converters or muffler. On a gas truck you should have enough tape to wrap the whole pipe over the rear tire. I don't think its necessary to go any further. Next start the truck and let the hot exhaust dry off all of the wet wrap. Shut the truck down and let it completely cool down. Now paint the wrap with the special paint. This will help seal the porosity of the tape against the elements.
Next stuff some Fiberglas up into the parking brake lever hole from the bottom. Next I cut the Thermo-Tec Heat barrier in half. I shoved one half up against the firewall behind the exhaust manifold facing the aluminum toward the engine. I had to remove the drivers side air cleaner and pull the sheet up. I tucked one bottom edge of the sheet under a line between clamps that run along the inside of the frame rail. The second sheet was carefully stuffed over the transmission and pulled forward to meet the first sheet. Be careful not to obstruct the linkages and oxygen sensor. These sheets will effectively insulate the cabin from noise and heat with the added protection of keeping the elements off the wires and lines running along the bottom of the body.
Step 3 (on a wagon) is to remove the rear carpet and plywood by unbolting the 4 cargo tiedowns. Cut to size and lay in the Heat Shield insulation from Warshawsky aluminum side down. Find the four holes in the floor and cut or drill out holes in the insulation. Place the plywood /carpet assembly back in and bolt down.
Step 4 is to take out the glove box by removing the screws and pulling the box out of the front console. What you're going to find is a giant chamber which could be used for things like a bigger glove box, a CB radio etc. Take wads of Fiberglas insulation and lightly stuff all of the space toward the front and sides. Don't pack insulation around anything that needs to get rid of heat like the radio and electronics. I also found that when the fan for the auxiliary heater and cooler was running, tons of air was being leaked from the center console into the front console at the bottom where the two meet. By stuffing insulation into the bottom crack I reduced the wasted airflow significantly. Don't close off the air all the way. In really hot weather it probable won't hurt to circulate some air to cool the electronics within. Next open the trap door where the fuse box is located by the drivers feet. Stuff insulation all the way back to the fire wall and along the sides of the truck. I also stuffed some Fiberglas into voids in the firewall on the engine side.
I can now talk to my wife and yell at my kids and they hear me. When traveling at 60 mph on the highway I can hear the radio with the volume at 12. I also reaped a couple of other rewards. The exhaust wrap not only reduces the noise but reduces the heat radiated into the cabin. Thermo-Tec claims that keeping the exhaust gases from cooling, the exhaust gas velocity can remain high thus improving the scavenging effect and increasing horsepower. I thought the claim was baloney until I actually drove the truck for the first time after installing the wrap. I actually noticed a snappier throttle response. By keeping the exhaust system warmer longer after shutting down, moisture will evaporate causing less exhaust system corrosion.
When I get the motivation I'm going to look into the following. Insulate the 8 cargo tiedowns bolts from the bottom with spray foam. When I was in the desert heat I almost got burned touching one of the tiedown bolts. Insulate the roof and put on a sound absorbing headliner. Installing a sound absorbing headliner will of course mean the ceiling will be harder to clean up if it gets dirty. We were in Scottsdale this summer and found that the air conditioner was only good to about 97 degrees during the day. Warmer then that the heat gain from the roof puts out more BTU's then the air conditioner. I would recommend that anyone living in the desert at least put a layer of insulation between the roof and the headliner. My next suggestion is a hood blanket. The Heat Shield insulation from Warshawsky can be cut to fit under the hood and plastic hood blanket fasteners (get them at an auto supply house) can be fastened to the hood stiffeners. It should be possible to pop rivet a stiff fiber material in the wheel wells with a sound deadening backing to reduce the tire noise. All of this stuff should not affect your warranty. My next idea will. You can reduce noise and gain fuel mileage by replacing the clutch controlled cooling fan with a thermostatically controlled electric fan. But, I don't want to get started on this subject. Good luck !!!
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